1. Field of the Invention
This invention relates generally to spark plugs, and more particularly to lateral firing spark plugs and spark plugs having electrode configurations that allow the spark to selectively fire across the path of least resistance.
2. Brief Description of the Prior Art
A conventional spark plug for combustion engines has a center electrode embedded in a ceramic insulator and an outer, inverted L-shaped grounding electrode spaced from the outer tip end of the center electrode by a narrow gap. The spark jumps across the gap between the center electrode and the grounding electrode.
The convention spark plug requires frequent replacement under normal wear for several reasons. Over a period of time, the optimal gap between the two electrodes is altered due to wear and pitting caused by the repeated high voltage firing. Wear and pitting increases the electrical potential needed for discharge and often results in weak sparks and failure to spark when required. Carbonization and the depositing of lead, lead oxide, and other contaminants in and around the electrodes during the course of repeated electrical discharges also alter the dimensions of the spark gap and reduces the life of the plug, reduces engine efficiency, and increases fuel consumption.
There are several patents that disclose spark plugs that have an annular ground electrode.
Franks, U.S. Pat. No. 3,958,144 discloses spark plugs having an annular grounding electrode that provides a number of alternate sparking paths wherein both electrode surfaces are formed of alloy consisting of 75% nickel, 15% chromium, 5% iron, and the remainder copper.
Lindsay, U.S. Pat. No. 4,730,582 discloses a spark plug for having an annular ground ring with a circular opening surrounding the center electrode. The ground ring may include a series of ports to facilitate disbursement of the ignited fuel/air mixture from the spark plug.
Kagawa, et al, U.S. Pat. No. 4,914,343 discloses a spark plug having an outer electrode configured as a flat plate vertically spaced from the tip end of the center electrode by a plurality of spider legs with a plurality of holes formed in the plate to improve the plug durability and retard any discharge voltage increases.
Johnson, U.S. Pat. No. 5,280,214 and Smith, U.S. Pat. No. 5,408,961 disclose spark plugs having a circular or semi-circular ring shaped ground electrode supported by one or more mounting posts in vertically spaced relation from the tip end of the center electrode or surrounding the center electrode.
Buhl, U.S. Pat. No. 5,623,179 discloses a spark plug having diagonally disposed electrode projections or elements extending from a central electrode through V-shaped or elliptical grounding windows or apertures formed in a cylindrical outer grounding electrode skirt.
Lindsay, U.S. Pat. No. 5,633,557 discloses an anti-fouling spark plug having an annular ground ring with a circular opening surrounding the center electrode. The inner diameter of the circular opening has a sharpened point. In another embodiment, the circular opening has a sawtooth configuration with the points of the sawtooth configuration facing radially inward toward the center electrode. The ground ring may include a series of ports to facilitate disbursement of the ignited fuel/air mixture from the spark plug.
Rossi, U.S. Pat. No. 5,892,319 discloses a top and side firing spark plug having a center electrode surrounded by a ground electrode wherein a large plurality of sharp edges such as screw threads, knurls, and various projections are provided on the center electrode, the ground electrode, or both. In one embodiment the ground electrode has a sawtooth configuration with the points of the sawtooth configuration facing radially inward toward the center electrode.
The present invention is distinguished over the prior art in general, and these patents in particular by a spark plug having a center electrode and surrounding ground electrode configuration that allows the spark to selectively fire across the path of least resistance. In one embodiment the plug has a cylindrical ground electrode with plural inverted V-shaped projections at its outer end that face outwardly from the end of the electrode. The side wall of the ground electrode may be provided with apertures to facilitate radial gas flow. In another embodiment the ground electrode has plural spherical projections at its outer end. In another embodiment the ground electrode is a cylindrical foraminous configuration with inverted V-shaped projections at its outer end. In another embodiment the center electrode has a spherical outer end encircled by and a cylindrical ground electrode. In another embodiment the center electrode has a spherical outer end surrounded by a hemispherical foraminous dome-shaped ground electrode.
It is therefore an object of the present invention to provide a spark plug having novel and improved electrode configurations.
It is another object of this invention to provide a spark plug having an extended lifetime.
Another object of this invention is to provide a spark plug with center and ground electrodes having greatly improved resistance to wear, pitting and physical deterioration.
Another object of this invention is to provide a spark plug having a ground electrode configuration with a plurality of grounding electrode projections that enable the spark from a center electrode to selectively fire across the path of least resistance.
Another object of this invention is to provide a spark plug having a center electrode and ground electrode configuration that will increase fuel economy and increase engine efficiency.
Another object of this invention is to provide a spark plug having a center and ground electrode configuration that reduces accumulation of contaminating deposits on the electrodes during operation.
A further object of this invention is to provide a spark plug with a center electrode and ground electrode configuration that will reduce exhaust emissions.
A still further object of this invention is to provide a spark plug with a novel center electrode and grounding electrode configuration that can be manufactured inexpensively from conventional materials.
Other objects of the invention will become apparent from time to time throughout the specification and claims as hereinafter related.
The above noted objects and other objects of the invention are accomplished by a spark plug having a center electrode and surrounding ground electrode configuration that allows the spark to selectively fire across the path of least resistance. In one embodiment the plug has a cylindrical ground electrode with plural inverted V-shaped projections at its outer end that face outwardly from the end of the electrode. The side wall of the ground electrode may be provided with apertures to facilitate radial gas flow. In another embodiment the ground electrode has plural spherical projections at its outer end. In another embodiment the ground electrode is a cylindrical foraminous configuration with inverted V-shaped projections at its outer end. In another embodiment the center electrode has a spherical outer end encircled by and a cylindrical ground electrode. In another embodiment the center electrode has a spherical outer end surrounded by a hemispherical foraminous dome-shaped ground electrode.